Full-spectrum flash for electronic devices
Introduced here are light sources for flash photography configured to produce high-fidelity white light that is tunable over a broader range of correlated color temperatures (CCTs) than conventional flash technologies. The light source can include multiple independently controllable color channels representing illuminants (e.g., light-emitting diodes) of different colors with varying degrees of saturation. Operating collectively, the multiple color channels can produce a high spectral quality white light corresponding to different CCTs (e.g., “warm” white light having a red hue, “cool” white light having a blue hue). Operating independently, these same color channels can be pre-flashed in a variety of prescribed sequences to probe the spectral characteristics of a scene, thereby allowing for an enhanced, spectrally matched white flash as well as collecting per-pixel reflectivity data that can be later used in during post processing of the captured image.
1. A light source comprising:
an illuminant array that includes at least three color channels,
wherein each color channel includes one or more illuminants configured to produce a substantially similar color, and
wherein each color channel is separately addressable to produce light of a different color; and
a controller configured to:
identify a color mixing model associated with a correlated color temperature (CCT) among multiple color mixing models based on a characteristic of an image sensor that is responsible for generating an image in conjunction with the at least three color channels being driven simultaneously, and
drive, based on the color mixing model, the at least three color channels to produce white light having the CCT,
wherein the color mixing model specifies how much current is to be provided to each color channel of the at least three color channels.
2. The light source of claim 1 , wherein each color mixing model of the multiple color mixing models is associated with a different CCT.
3. The light source of claim 1 , wherein the multiple color mixing models are stored in a memory that is accessible to the controller via a network.
4. The light source of claim 1 , further comprising:
at least three linear field-effect transistor-based (FET-based) current regulated drivers,
wherein each linear FET-based current regulated driver is configured to drive a corresponding color channel of the at least three color channels.
5. The light source of claim 1 , further comprising:
a heat sensor configured to measure thermal feedback;
wherein the controller is further configured to:
determine, for each color channel, an effect of the thermal feedback, and
adjust the color mixing model responsive to a determination that the effect exceeds a predetermined threshold for at least one color channel.
6. The light source of claim 1 , further comprising:
multiple optical sensors configured to measure optical feedback at different wavelengths;
wherein the controller is further configured to:
determine, for each color channel, whether color shift has occurred by examining the optical feedback, and
adjust the color mixing model responsive to a determination that color shift exceeds a predetermined threshold for at least one color channel.
7. The light source of claim 1 , further comprising:
a substrate comprised of a material able to dissipate heat generated by the illuminant array that is mounted thereon.
8. The light source of claim 7 , wherein the substrate has a diameter of less than four millimeters (mm).
9. The light source of claim 7 , wherein the substrate is comprised of woven fiberglass cloth with an epoxy resin binder, ceramic, metal, or any combination thereof.
10. A light source comprising:
an illuminant array that includes multiple color channels,
wherein each color channel includes one or more illuminants configured to produce a substantially similar color, and
wherein each color channel is separately addressable to produce light of a different color;
multiple linear field-effect transistor-based (FET-based) current regulated drivers,
wherein each linear FET-based current regulated driver is configured to drive a corresponding color channel of the multiple color channels; and
a controller configured to:
identify a color mixing model associated with a correlated color temperature (CCT) among multiple color mixing models based on a characteristic of an image sensor that is responsible for generating an image in conjunction with the multiple color channels being driven simultaneously, and
drive, based on the color mixing model, the multiple color channels via the multiple linear FET-based current regulated drivers to produce light having the CCT,
wherein the color mixing model specifies how much current is to be provided to each color channel of the multiple color channels.
11. The light source of claim 10 , further comprising:
a heat sensor configured to measure thermal feedback;
wherein the controller is further configured to:
determine, for each color channel, an effect of the thermal feedback, and
adjust the color mixing model responsive to a determination the effect exceeds a predetermined threshold for at least one color channel.
12. The light source of claim 10 , further comprising:
multiple optical sensors configured to measure optical feedback at different wavelengths;
wherein the controller is further configured to:
determine, for each color channel, whether color shift has occurred by examining the optical feedback, and
adjust the color mixing model responsive to a determination that color shift exceeds a predetermined threshold for at least one color channel.
13. The light source of claim 10 , further comprising:
a substrate comprised of a material able to dissipate heat generated by the illuminant array that is mounted thereon,
wherein the substrate has a diameter of less than four millimeters (mm).
14. The light source of claim 13 , wherein the substrate is comprised of woven fiberglass cloth with an epoxy resin binder, ceramic, metal, or any combination thereof.
15. A light source comprising:
an illuminant array that includes at least three channels,
wherein each channel includes one or more illuminants configured to produce electromagnetic radiation at a same wavelength, and
wherein each channel is separately addressable to produce electromagnetic radiation at a different wavelength;
a controller configured to:
select a model from amongst multiple models based on a characteristic of an image sensor that is responsible for generating an image in conjunction with the at least three channels being driven simultaneously, and
drive the at least three channels simultaneously in accordance with the model, so as to produce light that visibly corresponds to a given wavelength, wherein the model governs how much current is to be provided to each channel to produce the light,
wherein none of the at least three channels is able to individually produce electromagnetic radiation at the given wavelength.
16. The light source of claim 15 , wherein the characteristic is thermal feedback generated by a heat sensor or optical feedback generated by an optical sensor.
17. The light source of claim 15 , wherein each illuminant in each channel corresponds to a different semiconductor die, and wherein the intra-die spacing is no more than 0.1 millimeters (mm).